Tyre sizes/ Wheel sizes / GU Patrol

G'day All,
I've just purchased a 3.0TD 5 speed GU Patrol with 5.5" splitties and 235/85r16 Bridgestone Desert Dueller 661's. I've encountered what I believe is a fairly common problem with the wheel balance. I get a shudder at 85-95km/h. I've been to a reputable suspension expert and the alignment is good. The wheels need pretty massive weights to get them close to balanced.

I'm thinking of trying to find a set of solid 16x7 rims - possibly steel Prado rims. Has anyone used these on a Patrol ? The offsets look OK ?

I'm also toying with the idea of 255/85/R16 tyres, the reason being I do a lot of cruising at free way speeds during the week and most of my offroad driving is on gravel roads. I'm guessing the taller tyres will work in my favour by increasing the gearing by 4-6% and also giving me a bit more room under the diffs. I don't do much real hard 4WD'ing, nor do I tow, nor carry really heavy loads that often. I don't really want a wider tyre like a 275. I know 255/85 it's an uncommon tyre size but I'm in the habit of going bush with two spares and a tyre repair kit so I reckon I'll get away with that part of the equation.

Has any one used this sized tyres on a GU 3.0TD ?

Or should I just stick with the 235's.

Thanks.